Electrostatic photographic copying apparatus

ABSTRACT

An electrostatic photographic copying apparatus comprising a frame member having a transparent plate on which to place an original to be copied, a rotatable photosensitive drum having an electrostatic photographic material on its periphery, an optical system for projecting an image of the original onto the surface of the photographic material, an image-forming zone disposed exteriorly of, and alongside, the periphery of said photosensitive drum for forming on said sensitive material an electrostatic latent image corresponding to the image of the original or a developed image corresponding to the latent image, a transfer zone for transferring said image to a transfer paper, and a transfer paper forwarding system for feeding the transfer paper on which the image has been transferred to a discharge end through a desired treating zone.

United States Patent Washio et al. 1 1 Dec. 2, 1975 [54] ELECTROSTATICPHOTOGRAPHIC 3,635,554 1/1972 Hodges 355/8 COPYING APPARATUS 3,689,1469/1972 Ito et al. 3,784,297 1/1974 [to et a1 355/3 R [75] Inventors:TakaJi Washio, Toyonaka; Koichi Sasakl; (Tatsuo Alzawa both of PrimaryExaminerRobert P. Greiner Osaka of Japan Attorney, Agent, or FirmSherman& Shalloway [73] Assignee: Mita Industrial Company, Ltd.,

Osaka, Japan [57] ABSTRACT [22] Filed: Sept. 21, 1973 An electrostaticphotographic copying apparatus comprising a frame member having atransparent plate on [21] Appl' 399516 which to place an original to becopied, a rotatable photosensitive drum having an electrostatic photo-[30] Foreign Application Priorit D t graphic material on its periphery,an optical system for Sept. 24 1972 Japan 47-95460 Projecting image ofthe Original Onto the surface of the photographic material, animage-forming zone dis- 52 US. Cl ass/3 R; 355/8' 355/14 Posedexteriorly and alongside the Periphery f [51 1 Int. Cl. G03C /00 Saidphoto'sensitive drum for forming on said sensitive .[58] Field of SearchH 355, R, 8, 1 1, 14, 50, material an electrostatic latent imagecorresponding to 355/51 66 the image of the original or a developedimage corresponding to the latent image, a transfer zone for trans- [56]References Cited ferring said image to a transfer paper, and a transferpaper forwarding system for feeding the transfer paper UNITED STATESPATENTS on which the image has been transferred to a disgrztlvesnkwl.355/3 R charge end through a desired treating Zone. u us e a 3,399,6109/1968 Eichorn 355/8 8 Claims, 16 Drawing Figures a ill? 9 5 424 48 4848" I5 o '1 & 7 "45A 3? I2- 23 38 44' '3' i n 274 45B 29\3O .i' fit 7 I/23 4 26kg 3O 4 Q b 5 43 b 3 14,

35f) 1 3| 35 n I b 5| 24 5 35f 35c 35 US. Patant Dec. 2, 1975 Sheet 2 of11 U.S. Patent Dec.2,1975 Sheet40f1l 3,923,391

2, 1975 Sheet 5 of 11 3,923,391

US. Patent Dec.

US. Patent Dec. 2, 1975 Sheet60fll 3,923,391

US. Patent Dec. 2, 1975 Sheet 8 of 11 3,923,391

Sheet 10 of 11 US. Patent Dec. 2, 1975 US. Patent D60 2, 1975 Sheet 11of 11 3,923,391

m m T5 3 F E ma ELECTROSTATIC PHOTOGRAPI'IIC COPYING APPARATUS SUMMARYOF THE INVENTION This invention relates to an improvement inelectrostatic photographic copying apparatus, and specifically to animprovement in an electrostatic photographic copying apparatus of thetype equipped with a rotatable photosensitive drum.

The conventional electrostatic photographic copying apparatus of thistype generally requires a synchronization control mechanism having acomplicated structure in order to expose an image of an original aphotosensitive drum synchronously with the rotation of thephotosensitive drum, and in order to a transfer paper synchronously withthe rotation of the photosensitive drum. Furthermore, it is necessary toprovide an electrical charging mechanism or an exposing section for anoptical system, etc. along the circumference of the photosensitive drum.These provisions tend to increase the size of the apparatus.

It is an object of this invention to provide an electrostaticphotographic copying apparatus in which the exposure of images can beeffected synchronously with rotation of a sensitive drum by means of adevice having a relatively simple structure.

Another object of this invention is to provide an electrostaticphotographic copying apparatus in which the photosensitive drum and atransfer paper can be moved in exact synchronization with each other bya device having a relatively simple structure.

Still another object of this invention is to provide an electrostaticphotographic copying apparatus which includes a cut length adjustingdevice having a relatively simple structure whereby a continuous web oftransfer paper can be cut exactly according to the required copyinglength of the original.

A further object of this invention is to provide an electrostaticphotographic copying apparatus which is relatively compact.

According to this invention there is provided an electrostaticphotographic copying apparatus comprising a frame member having atransparent plate on which an original to be copied is placed, arotatable photosensitive drum having electrostatic photographic materialon its periphery, an optical system for projecting an image of theoriginal onto the surface of the photographic material, an image-formingzone disposed exteriorly of, and alongside, the periphery of saidphotosensitive drum for forming on said sensitive material anelectrostatic latent image corresponding to the image of the original ora developed image'corresponding to the latent image, a transfer zone fortransferring said image to a transfer paper, and a transfer paperforwarding system for feeding the transfer paper on which the image hasbeen transferred to a discharge end through a desired treating zone.

This invention can be applied to any electro-static photographic copyingmachine of the type in which a photosensitive drum is provided in amachine housing and transfer paper is brought into contact with thephotosensitive drum to thereby transfer the image from thephotosensitive drum to the transfer paper. For instance, this inventioncan be applied to either a copying machine of the so calledoriginal-moving, slit-exposure type in which an original to be copied issupported on a transparent plate mounted movably in the machine housingand an optical system is fixed in the housing, or the so called opticalsystem-moving type in which an original is supported on a transparentplate fixed in the machine housing, while the optical system is moved toeffect the slit exposure. In addition, this invention can be applied toa copying machine of the so called static image-transferring type inwhich an electrostatic image is formed on the surface of aphotosensitive layer of a photosensitive drum, transferred to transferpaper and then visualized, or to a copying machine of the so calledtoner image-transferring type in which an electrostatic image formed onthe surface of a photosensitive drum is developed with a toner and thetoner image is transferred to transfer paper and, if required, fixed.

This invention can also be applied to a copying machine of the type inwhich transfer paper is fed in a separate sheets or from a web-like formas withdrawn from a paper roll. For instance, this invention can beapplied to a copying machine of the type in which a container orcartridge of transfer paper sheets is provided on one end wall of themachine housing and transfer paper sheets are automatically fed fromsuch container or cartridge, or to a copying machine of the type inwhich transfer paper sheets are manually fed into a passage fortransportation of transfer paper sheets.

Accordingly, this invention will be described hereinafter mainly withreference to embodiments in which this invention is applied to a copyingmachine of the original-moving, toner image-transferring type, but itmust be noted that the application is not limited to such application.

This invention will now be illustrated in more detail by reference toembodiments shown in accompanying drawings.

FIG. 1 is an arrangement diagram illustrating the outline of the copyingmachine of this invention.

FIG. 2 is a sectional side view in which the optical system and staticimage-forming zone of the copying machine of FIG. 1 are illustrativelyenlarged.

FIG. 3 is an enlarged sectional side view illustrating an embodiment ofthe developing apparatus usable in the copying machine of thisinvention.

FIGS. 4 and 5 are diagrams illustrating the arrangement and function ofthe magnet mechanism used in the developing apparatus of FIG. 3.

FIG. 6 is a side view illustrating the arrangement of the developingcounter pole used in combination with the developing apparatus of FIG.3.

FIG. 7 is a perspective view illustrating a toner supply cartridge usedin the developing apparatus of FIG. 3.

FIG. 8-A is a simplified side view of the transfer apparatus used in thecopying machine of this invention.

FIG. 8-B is an enlarged sectional side view of the fixation zone of thecopying machine of this invention.

FIG. 9 is a diagram illustrating the principle of the copying machine ofthis invention.

FIG. 10 is an arrangement view of various control mechanisms used in thecopying machine of this invention.

FIG. ll-A is an arrangement view showing the driving system of thecopying machine of this invention.

FIG. 11-3 is a sectional view showing the system for driving the movingframe.

FIG. ll-C is a perspective view illustrating the restraint mechanism forthe moving frame.

FIG. l2-A and l2-B are wiring diagrams of the electric circuit of thecopying machine of this invention.

ENTIRE STRUCTURE In FIG. 1 illustrating an outline of the entirearrangeexposure mechanism '11 and the entire surface exposure mechanism12 maybe omitted. Furthermore,

ment in the electrostatic photographic copying masupported by a movingframe 3 capable of moving reciprocatingly in the horizontal directionand an original-pressing flexible plate 4 is attached to the movingframe 3 so that it can cover the transparent plate 2. In the interior ofthe housing 1, a photosensitive drum 6 having on the surface thereof aelectrostatic photosensitive layer is rotatably mounted. Thisphotosensitive layer 5 may be any of a monolayer photosensitive plateformed by applying an inorganic photoconductor such as selenium, zincoxide, cadmium sulfide, or cadmium selenide or an organic photoconductorsuch as polyvinyl carbazole, optionally together with a binder, on asubstrate such as a metal plate or a paper rendered electricallyconductive, a multilayer photosensitive plate formed by laminating aplurality of photoconductor layers or a sandwich-type multilayerphotosensitive plate forming by inserting a photoconductor layer betweenan insulator layer and a conductor layer.

An image-forming zone 7 and a transfer zone 8 are grouped along theperipheral surface of the photosensitive drum 6. In the embodiment shownin FIG. 1 where a sandwich-type multilayer photosensitive plate formingby inserting a photoconductive layer between an insulating layer and aconductor layer is employed and the toner image transfer is effected,the image-forming zone 7 comprises a static latent image-forming areaincluding a preliminary electrification mechanism 9 for erasing thecharge remaining on the surface of the photosensitive layer, a primaryelectrification mechanism 10 for charging the surface of thephotosensitive layer with a specific polarity, a secondaryelectrification and simultaneous exposure mechanism 11 for effecting thesecondary electrification while an image is being exposed on theprimarily electrified photosensitive layer and an exposure mechanism 12for exposing to light the entire surface of the secondarily electrifiedand imagelight-exposed photosensitive layer, and a developing areaincluding a development'mechanism 13 for developing the electro-staticlatent image with a toner powder. Each of the foregoing electrificationmechanisms includes a corona wire on which a high voltage is applied,and the photosensitive layer is electrified by the corona discharge fromthis corona wire. The secondary electrification and simultaneousexposure mechanism 1 1 comprises an optical passage 14 connecting thephotoconductive layer 5 optically with an opening for exposing thephotosensitive layer to light and a corona wire 15 in said opticalpassage 14, on which a high voltage is applied. The voltage to beapplied on the 15 of the secondary electrification and simultaneousexposure mechanism 11 may be a direct current voltage of a polarityreverse to the polarity of the primary electrification, an alternatingcurrent voltage or an asymmetric alternating current voltage.

The toner powder development mechanism 13 may be of any desired typesuch as for example, a magnetic brush type, a cascade type or a powdercloud type.

When the photoconductive layer 5 is composed of a monolayerphotosensitive plate, the charging element 15 of the secondaryelectrification and simultaneous where the electro-static image on thephotosensitive layer 5 is directly transferred to transfer paper (in thecase of electro-static image transfer), the development mechanism 13need not be provided along the periphery of the photosensitive drum 6.

An optical system indicated as a whole by reference numeral 16 isprovided to project an image of the original a supported on thetransparent plate 2, onto the photosensitive layer 5 in theabove-mentioned imageforming zone. This optical system 16 comprises anopening 17 mounted in the upper portion of the housing 1 to expose theoriginal to light, a light source 18 for illuminating the original a tobe copied, a photosensitive layer-light-exposing opening 19 provided inthe vicinity of the photosensitive layer 5 of the photosensitive drum inthe image-forming zone 7, and a group of reflex mirrors 20, 21 and amirror lens 22 provided to connect optically the original-light-exposingopening 17 with the photosensitive layer-light-exposing opening 19 andto form a reverse image of the original a to be copied on thephotosensitive layer 5.

Along the periphery of the photosensitive drum 6, the transfer zone 8 isdisposed in succession to the image-forming zone 7. In the housing 1 apassage for transfer paper b (indicated as a whole by reference numeral23) is provided so that said passage is circum-. scribed with thephotosensitive drum 6 in the transfer zone 8. At the upstream end ofthis transfer paper passage 23, a transfer paper feed mechanism ismounted. For instance, in the embodiment illustrated in FIG. 1, a rollstand 25 supported rockably on the machine housing by means of a fulcrum24 is mounted on the upstream end of the transfer paper passage 23, anda shaft 28 of a reel 27 is removably and rotatably mounted on a fittingrecess 26 formed on the upper end of this roll stand 25.

Downstream of the reel 27, there are provided both a guide roller 29 anda pair of driven feed rollers 30, 30 provided with a roll paper feedingclutch C2 in order to introduce transfer paper from a transfer paperroll b wound on the shaft of the reel 27. A pair of transferpapertransporting rollers 31, 31 which are normally driven are disposedbetween the feed rollers 30, 30 and the transfer zone 8, and a transferpapercutting mechanism 32 is mounted between the feed roller 30, 30 andthe transfer paper-transporting rollers 31, 31'.

This transfer paper-cutting mechanism 32 includes a stationary blademember 33 and a rotary blade member 34. The rotary blade member 34 isrotated by excitation of a cutter solenoid and cuts transfer paper bpassing through the stationary blade member 33 and rotary blade member34. Accordingly, the position (Pl) shown in FIG. 9 and 10 for actuationof the transfer paper-cutting mechanism is the position of the upperedge of the stationary blade member 33. In the non-actuated state, theblade of the rotary blade member 34 is positioned on the upper side ofthe transfer paper passage between the feed rollers 30, 30' and thetransporting rollers 31, 31' so that it does not intersect the transferpaper passage. In this invention, as will be detailed hereinafter, theposition of the leading edge of transfer paper atthe beginning offeeding and the position for stoppage and standing-by of the leadingedge of rolllike transfer paper cut are set at the position (Pl) foractuation of the transfer paper-cutting mechanism. In

order to attain this feature, upper and lower guide plates 35a and35'a'are disposed between the cutting mechanism 32 and feed rollers 30,30, and another upper and lower guide plates 35b and 35b, between thecutting mechanism 32 and transporting rollers 31, 31, so that lowerguide plates 35a and 35b are positioned in an almost straight line withthe upper edge of the stationary blade member 33 and the upper guideplates 35a and 35b are positioned in an almost straight line with thelower edge of the rotary blade member 34 in the non-actuated state. Theforegoing structures make it possible to conduct the transportation andstoppage of transfer paper smoothly without occurrence of paper jammingor other troubles. Further downstream of the normally driven,transporting rollers 31, 31, there are provided upper and lower guideplates 35c and 350' to introduce transfer paper b into the transfer zone8.

In the embodiment of the copying machine in FIG. 1, a paper feedmechanism for feeding a sheet-like transfer paper b is providedindependently of the paper feed mechanism for feeding a roll-liketransfer paper. More specifically, a paper-feeding table 51 is providedopenably or removably at the end of the machine housing 1 at theupstream end of the transfer papertransporting passage 23 to feed asheet-like transfer paper b", and at the tip of this paper-feedingtable, there are mounted a paper sheet feeding opening 52 and upper andlower guide plates 35d and 35'd connected to this opening 52. A pair ofpaper sheet feed driven rollers 53, 53 provided with a sheet paper feedclutch C3 (shown in FIG. 11-A) are mounted downstream of the upper andlower guide plates 35d, 35d. Between said sheet paper feed rollers 53,53 and the abovementioned transfer paper-transporting rollers 31, 31',upper and lower guide plates 35e and 35'e, a pair of sheet-transportingrollers 54, 54 and upper and lower guide plates 35f and 35]. are mountedto transport sheet-like transfer paper b" to said rollers 31, 31 In thecopying machine illustrated in FIG. 1, the above-mentioned transferpaper-transporting passage 23 is circumscribed with the photosensitivedrum 6 in the transfer zone 8 and forms almost one plane extending fromsheet-transporting means 53, 53' to the abovementioned fixation zone 46.This passage 23 for feeding roll-like transfer paper b joins a passage23' for feeding sheet-like transfer paper b" in the position oftransporting rollers 31, 31' disposed upstream of the transfer zone 8,and transfer paper is then forwarded through the common transferpaper-transporting passage 23, extending in a straight line. When thepassage for transporting a sheet-like transfer paper is thus disposed ina straight line in the machine housing and is circumscribed with thephotosensitive drum 6 in the transfer zone 8, even if a very thin orsoft paper, cloth, film or foil is used as the sheet-like transfer paperb, paper jamming can be greatly reduced and the copying operation can beaccomplished very assuredly.

Further, if paper jamming is caused to occur in the transferpaper-transporting passage of the copying machine, removal of the jammedpaper can be facilitated by disposing openably or dismountably each ofmembers positioned in the transporting passage except for some pairs oftransporting rollers. For instance, the roll-like transfer paper-cuttingmechanism 32 and guide plates 35a, 35a, 35b, 35b positioned between theroll-feeding rollers 30, 30 and transporting rollers 31, 31, and guideplates 35f, 35] positioned between the transporting rollers 54, 54 andtransporting rollers 31, 31 are integrally attached to a supportingframe 55 mounted detachably on the frame of the machine housing 1. Thus,the jamming of paper can easily be inspected by dismounting theforegoing members together with the supporting frame 55. Similarly,guide plates 35e, 35e positioned beteween the sheet-like transferpaper-transporting rollers 53, 53' and the transporting rollers 54, 54'are integrally attached to a supporting frame 56 mounted dismountably onthe frame of the machine housing 1, so that these plates can bedismounted from the machine housing together with the supporting frame56. The foregoing structure makes it possible to check jamming oftransfer paper in the transfer paper-transporting passage with ease.

In the transfer zone 8, a transfer mechanism 36 is disposed to bringtransfer paper b into contact with the photosensitive layer 5 of thephotosensitive drum 6 and thereby transfer the image onto the transferpaper. This transfer mechanism 36 is constructed of a transfer rolleralone or in combination with a corona discharge mechanism. For instance,when the image to be transferred is an electrostatic image, it may betransferred onto transfer paper merely by contacting it with theelectrostatic image-carrying photosensitive drum by means of a roller.Of course, in this case, the transfer of the electrostatic image can beaccomplished effectively by forming an electric field between thetransfer roller and the substrate of the photosensitive drum or byeffecting the corona discharge from the back face of transfer paper.When the image to be transferred is a toner image, it may be transferredonto transfer paper by contacting it with the toner image-carryingphotosensitive drum by means of the transfer roller or by static forceand forming an electric field between the transfer roller and thesubstrate of the photosensitive drum or effecting the corona dischargefrom the back face of the transfer paper.

The transfer papentransporting passage indicated as a whole by referencenumeral 23 extends downstream of the transfer zone 8. On the dischargeside the transfer zone of, and adjacent to the photosensitive drum 6there is provided a peeling mechanism 37 which removes transfer paper bfrom the photosensitive layer 5 of the photosensitive drum 6 and directsit toward the said transporting passage. This peeling mechanism 37 isprovided with a peeling projection 38 disposed so that its leading edgebrought into contact with the photosensitive layer of saidphotosensitive drum. Said peeling projection 38 peels off the leadingedge of the transfer paper b from the photosensitive layer surface andguides the transfer paper b to the transfer papertransporting passage. Afan 40 provided with a projection nozzle 39 directed toward the peelingprojection 38 is disposed to assist peeling of the transfer paper b fromthe photosensitive layer surface and introduction of transfer paper binto the transfer paper-transporting passage and to accomplish theseoperations stably and assuredly.

In position spaced from the peeling mechanism 37 along the direction ofrotation of the rotary drum 6, there may be provided a cleaningmechanism 41 to clean the photosensitive layer of the photosensitivedrum 6 by removing the toner from the surface thereof.

' This cleaning mechanism 41 comprises a roller 42 provided with arubber or brush surface which is rotated while in contact with thephotosensitive layer of the drum 6. In the case of electro-static imagetransfer, of course, this cleaning mechanism may be omitted.

The transfer paper-transporting passage 23 extending to the downstreamof the transfer zone 8 is provided with pair of driven rollers or one ormore endless belts and it transports transfer paper through a subsequenttreating zone. The treating zone may be an imagefixing zone, when atoner image is transferred and may include development and fixing zoneswhen a static image is transferred. In the embodiment shown in FIG. 1,an endless belt 45 supported and driven by a driving pulley 43 anddriven pulleys 44, 44 is mounted to define the lower side of thetransfer paper-transporting passage 23 on the upper side of the transferpapertransporting passage 23, a fixation mechanism 46 is disposed to fixthe toner image on transfer paper b. This fixation mechanism 46 includesan infrared lamp or electric heater 47 and the fixation of the tonerimage is accomplished by meltbonding it to transfer paper with heat fromthe heater. In order to prevent transfer paper from making directcontact with the fixation mechanism, another guiding belt 49 may bemounted on the upper side of the transfer paper-transporting passage 23.The guiding belt 49 is driven and supported by a driving pulley 48 anddriven pulleys 48', 48", 48". It is also possible to position pulleys44' and 48' supporting belts 45 and 49 near the discharge end 203 of thepassage 23 in a manner such that the pulleys 44 and 48' contact eachother through the belts, whereby transfer paper on which the image hasbeen formed can be discharged assuredly from the fixing zone. Inaddition, on the lower side of the transfer papertransporting passage23, a suction mechanism 50 may be provided to suck transfer paperthrough the endless belt 45, whereby transfer paper will adhere closelyand fixedly to the endless belt 45. In this case, the guiding belt 49may be omitted. Instead of a combination of the infrared lamp orelectric heater with transfer papertransporting belts, a knowncombination (not shown) of an iron roller and a pressing roller may beused as the fixation mechanism 46 without disadvantages.

As is shown in FIG. 1, it is preferred that the photosensitive drum 6 belocated so that the uppermost part of its circumferential surface is inproximity to, and faces, the upper surface plate 201 of the machineframe 1. This is because by opening the upper surface plate 201, theinspection, repair, etc., of the photosensitive drum 6 can be veryeasily performed.

The transfer paper transporting passage 23 can be oriented substantiallyhorizontally in the lengthwise direction of the machine or it may beoriented in a plane inclined with respect to the lengthwise direction ofthe machine. However, as is shown in FIG. 1, it is preferred that thetransfer section 8 be located in a position which is at an angleexceeding 180C. in the direction of rotation of the photosensitive drumfrom the uppermost part of the photosensitive drum. Furthermore thetransfer paper transporting passage 23 form an upwardly inclined planeranging from the positions of transfer roller 33, 33 upstream of thetransfer zone 8 to the discharge end 201 through the transfer zone 8.This is because in the case of a copying machine provided with aphotosensitive drum, such numerous treating zones as preliminaryelectrification zone 9, primary electrification zone 10, secondaryelectrification and simultaneous exposure zone 11, exposure zone 12 anddevelopment zone 13 should be disposed alongside the peripheral surfaceof the photosensitive drum 6 from the transfer zone 8 in the directionopposite to the direction of rotation of the transfer drum 6, and onlypeeling zone 37 and cleaning zone 41 should be disposed along theperiphery of the photosensitive drum 6 from the transfer zone 8 in thedirection of rotation of the drum 6. As mentioned above, the transferpapertransporting passage 23 is provided to contact the photosensitivedrum 6 in an upwardly inclined state. Consequently a broad treatingspace can be obtained on the upstream side, that is the left side inFIG. 1, of the photosensitive drum 6. In addition to the above-mentionedvarious treating zones, the optical system and various paper feedmechanisms are provided above the feed side of the transfer zone 8, onlywhen the transfer paper-transporting passage is provided in the upwardlyinclined state, it is possible to secure a space sufficient to housethese mechanisms therein. Thus, in the embodiment of the copying machineof the invention illustrated in FIG. I, either the height or the lengthof the machine can be greatly shortened as compared with conventionalcopying machines of this type. Furthermore, since the transferpaper-transporting passage 23 is provided in the state upwardly inclinedwith respect to the direction of advance of transfer paper, a spacesufficient for opening the endless belt 45 downwardly can be providedbelow the fixing zone and hence, removal of jammed paper can beaccomplished with ease.

The foregoing embodiment of the copying machine of this invention hasthe following particular structure.

Optical System As shown in an enlarged sectional side view of FIG. 2,the optical system of the copying machine comprises a light source 18for light exposure, an opening 17 for exposing the original to light,two reflex mirrors 20 and 21, a mirror lens 22 and an opening 19 forexposing the photosensitive layer 5 to light, these members beingdisposed on partition walls 61, 62 and 63 or disposed so as toconstitute at least part of these partition walls. The opening 17 forexposing the original to light is disposed in the upper portion of themachine housing 1 so that when a moving frame 3 is positioned at a pointof initiation of light exposure, it can be optically connected to thestandard end point of initiation of light exposure (position P6 detailedhereinafter) which is formed on a transparent plate 2 mounted on themoving frame 3. This opening 17 may be shielded by a transparent plateor it may not be shielded by a transparent plate. The light source 18for light exposure is disposed on one 61 of partition walls 61, 62inserting the opening 17 therebetween, in the vicinity of said openingfor exposing the original to light. Alternatively, the light source 18may be disposed on both the partition walls 61 and 62. The opening 19for exposing the photosensitive layer to light is disposed in thepartition wall 62 positioned on the side of the photosensitive drum, andthe first reflex mirror 20 is mounted on the partition wall 63 of theoptical system while the second reflex mirror 21 and mirror lens 22 aredisposed on the partition wall 61 positioned on the opposite side. Thefirst reflex mirror 20 connects the opening 17 for exposure of theoriginal optically with the in-mirror lens 22 and simultaneouslyconnects the mirror lens 22 optically with the second reflex mirror 21.This second reflex mirror 21 is disposed in such a position that itconnects the first reflex mirror 20 optically with the opening 19 forexposing the photosensitive layer to light. In order to attain theforegoing positional relationship to the optical system, it is preferredthat the optical axis x of the mirror lens 22 be inclined from thehorizontal plane by a small angle (generally to 20) in the clockwisedirection, and the first and second reflex mirrors 20 and 21 be deviatedby an angle of 0 (generally +5 to +20) and 0 (generally 0 to in aclockwise direction from the position at an angle of 45 to thehorizontal plane in a counterclockwise direction.

In the optical system 16 of this embodiment, light projected from thelight source 18 and reflected from an original a to be copied isreflected by the first reflex mirror 20 and propagated to the mirrorlens 22. The light is then reflected from the surface of the mirror lens22, and is reflected again on the first and second reflex mirrors 20 and21 and propagated to the photosensitive surface 5 through the opening 19for exposing the photosensitive layer to light. Thus an image of theoriginal is formed on the photosensitive surface 5. As is seen from theforegoing explanation, in this optical system, by arranging the firstand second reflex mirrors and the in-mirror lens in an optical chamberso that a specific positional relationship as mentioned above can beattained among these optical members, it is made possible to utilize thefirst-reflex mirror in a duplicate manner for reflection and propagationof the light. As a result, a 4-fold optical passage for the reverseimage can be formed by a minimum unit combination of two reflex mirrorsand one mirror lens, and since the optical passage is of such 4-foldstructure, the space for the optical system can be greatly reduced.Further, since the number of members constituting the optical system isvery small, the angle determination in these members can be accomplishedvery easily. Preferably, the mirror lens 22 is mounted adjustably on thepartition wall 61 to permit easy adjustment of the focal point of theoptical system. By this contrivance, the focal point can be adjusted asdesired by adjusting the mirror lens 22 even when the height of thetransparent plate 2 for supporting an original to be copied or theposition of the photosensitive layer on the surface of thephotosensitive drum is varied.

In the embodiment illustrated in FIG. 2, the optical system 16 forms onechamber 64 substantially isolated from a static image-forming zone 7 anda developing zone 7 which are disposed along the passage for movement ofthe photosensitive layer 5. More specifically, each member of theoptical system 16 is disposed inside the partition walls 61, 62, 63 ormounted on such partition wall so that it will act as a part of thepartition wall. The opening 19 for light-exposing the photosensitivelayer is covered with a transparent plate 65 such as a transparent glassplate and is supported on partition side walls 62, 63 through a sealingpacking 66. Accordingly, in the area of the opening 19 of the opticalsystem 16, an optical connection is attained to the area of thephotosensitive layer 5 to be exposed while the air current isinterrupted. Alternatively, air may be positively passed into theelectrostatic image-forming zone 7' by providing an exhaust port of anexhaust gas duct 67 of a fan 40' on a side wall 1 of the machine housingconfronting the electrostatic image-forming zone 7.

In an electrostatic photographic copying machine of the type wherein thedevelopment is effected using a toner powder, the developing zone isgenerally disposed just below the zone for forming an electrostaticimage by electrification and light exposure. Therefore, operationaltroubles are brought about by scattering of the toner powder caused withrotation of the developing drum. When the side wall of the developingchamber is closely contacted with the photosensitive layer, theelectrostatic image formed on the surface of the photosensitive layer isdisturbed by friction. In order to prevent occurrence of this undesiredphenomenon, a certain clearance should be formed between the side wallof the developing chamber and the surface of the photosensitive layer.However, if such clearance is formed, a fine powder of the toner isscattered from this clearance and adheres to the electrification andlight exposure mechanisms of the electro-static imageforming zone,thereby contaminating these mechanisms. In the electrification zone,contamination is a special problem and is readily brought about byadsorption of the toner powder toner by the influence of staticelectricity generated by corona discharge. Thus, the image is disturbedin the optical system by scattering of the toner powder and a normaldischarge of the electrification mechanism is inhibited by the scatteredtoner powder.

In the embodiment illustrated in FIG. 2, the optical system 16 includinglens, mirrors and the like is so constructed as to form one chamber andthe area of the opening 19 for exposing the photosensitive layer tolight is kept in the air-tight state by the transparent plate 65.Therefore, intrusion of the toner powder into the optical system can beeffectively prevented. Furthermore since air is positively blown intothe static image-forming zone 7' including the electrification and lightexposure mechanisms and the pressure can be maintained in this zone 7'at a level higher than in the developing zone 7", scattering andintrusion of the toner powder into the electrostatic image-forming zonecan be prevented effectively. Thus, in the embodiment of the copyingmachine illustrated in FIG. 2, the need to frequency clean theelectro-static image-forming zone can be greatly reduced and clear copysheets can be obtained stably even if the copying machine is operatedfor a long period of time.

Developing Device The developing device used in the copying apparatus ofthis invention has such a structure as illustrated in FIGS. 3 to 7. InFIG. 3, the developing device shown generally at 13 includes adeveloping vessel 68 containing a developer, a stirring member 69 forstirring the developer, and a magnetic brush member 70 provided withinthe developer vessel 68. The developer may be composed of a toner powderand a magnetic carrier, or of a toner having magnetic properties. Whenthe developer is composed of the toner powder and magnetic carrier, thetoner powder is rubbed and electrically charged as a result of beingstirred by the stirring member 69.

As is illustrated in FIG. 4, this magnetic brush member 70 includes adevelopment sleeve 71 which is hollow and composed of a non-magneticsubstance and a magnet means 72 disposed in the stationary state in saiddevelopment sleeve 71. The magnet means 72 comprises a plurality ofmagnets 73 and 74 and a magnetism-intercepting member 75, which areprovided to satisfy the following positional and arrangementrequirements. The magnet forms a magnetic field sufficient to attract adeveloper to the sleeve surface and to retain the developer there in azone ranging in therotating direction of the sleeve from the position Pof pumping up the developer to the developing position P and themagnetism-intercepting member is disposed so that it weakens themagnetic field in at least a part of a zone ranging in the rotatingdirection of the sleeve from the developing position P,,, to theposition P of pumping up the developer. Preferably, the magnetic fieldformed by the magnet has a flux (f,, for example, about 1000 gauss)suitable for taking up the developer C at the pumping position P underthe sleeve 71, a flux (f about 700 gauss) substantially normal to thecircumferential surface of the sleeve at the developing position P and aconcentrated flux 02,) along the circumferential surface of the sleeveranging from the developer-pumping position P to the developing positionFor example, in the embodiment illustrated in FIG. 4, a first magnet(i.e., a magnet brush-forming magnet 73) is disposed so that one end 76of one pole N (or S) is directed to the developing position P,,. In theembodiment shown in FIG. 4, the magnetic brush-forming magnet 73 iscomposed of a plurality of rectangular magnet pieces bonded to oneanother, but of course, the magnet 73 may be composed of a single magnetpiece. I

On the side of the other end 77 of the magnetic brush-forming magnet73,a secondary magnet (i.e., a developer-pumping magnet 74) is disposed sothat its pole S (or N) is directed to the developer-pumping positionP,,. In this case, it is indispensable that the polarity of the actingpole of the magnetic brush-forming magnet 73 is contrary to the polarityof the acting pole of the developer-pumping magnet 74. Needless to say,this developer-pumping magnet 74 may be formed integrally with thebrush-forming magnet 73. It is preferred that these magnet brush-formingmagnet 73 and developer-pumping magnet 74 are so arranged that theirexciting directions are substantially perpendicular to each other.

The magnetism-shielding member 75 composed of a non-magnetized magneticmaterial (for example, nonmagnetic iron) is provided, as shown, so thatit weakens a magnetic field formed between the other pole S (or N) ofthe magnetic brush-forming magnet 73 and the developer-pumping magnet 74in the rotating direction of the sleeve.

By adopting the above-mentioned arrangement of the magnets 73 and 74 andthe magnetism-shielding member 75, the magnetic flux density can beheightened especially at the developing zone Pd to which the end 76 ofthe pole N of the magnetic brush-forming brush 73 is directed and at thedeveloper-pumping position P, to which the pole S of thedeveloper-pumping magnet 74 is directed. Furthermore, at the area of thedeveloping position Pd, a magnetic flux substantially vertical to thecircumference of the sleeve is formed, and moreover, a flux of arelatively high density, i.e., a concentrated flux, is formed betweenthe pole N of the magnet 73 and the pole S of the magnet 74, namelybetween the developer-pumping position P, and the developing position Palong the circumference of the sleeve. Since the polarity of the otherpole S of the magnetic brush-forming magnet 73 is the same as thepolarity of the acting pole S of the developer-pumping magnet 74 andsince the pole S of the magnet 73 and the space of portions of themagnet 74 other than the acting pole S are covered and filled with themagnetism-shielding member 75, the magnetic flux passes the interior ofthe magnetism-shielding member 75 between the pole S of the magnetic 73and the magnet 74, namely between the carrier-peeling position Pflocated on the opposite side of the developing position Pd and thedeveloper-pumping position P Hence, the magnetic flux density isextremely low on the circumference of the sleeve in such area.

In conducting the developing operation, the magnet mechanism 72 isarranged fixedly in the state shown in FIG. 4, and when the sleeve 71 isrotated in the counterclockwise direction, the developer c is applied tothe peripheral face of the sleeve at the developer-pumping position,whereby pumping of the developer is accomplished. The developer c istransported to the developing zone Pd while being carried on thecircumference of the sleeve. At the developing zone Pd, a magnetic brushof a high density uniformly extending vertically from the peripheralface of the sleeve is formed, and a close contact of this magnetic brushwith the electrostatic image carried on the photosensitive layer 5 canbe ensured. Thus, the electro-static image on the photosensitive layeris developed with the charge toner retained by the magnetic carrier. Thedeveloper which has completed the developing operation is rotated in thecounterclockwise direction from the developing position Pd while beingcarried on the circumference of the sleeve and is transported to thecarrier-peeling position Pf located on the opposite side of thedeveloping position Pd. At this carrier-peeling position Pf, the themagnetic flux density on the peripheral face of the sleeve isdrastically lowered and the developer 0' transported while beingretained on the circumferential face of the sleeve is peeled offtherefrom by the gravity and centrifugal force and is allowed to falldown on the bottom of a developer vessel 68. At the point of falling ofthe developer c, there is provided a stirring mechanism 69 which rotatesin the direction opposite to the direction of rotation of the sleeve,namely in the clockwise direction. This stirring mechanism 69 is mountedto stir the developer c having a lowered concentration of the tonerpowder with a freshly supplied toner powder and to feed a fresh supplyof the developer to the developer-pumping position after adjustment ofthe toner concentration. In the development apparatus of this embodimenthaving the foregoing structure, it is possible to form a clear tonerimage stably even after the operation has continued for a long time.

The surface of the developing sleeve 71 may be smooth or, in order toretain the developer thereon assuredly and easily, the surface can havea roulette, for example, a roulette with a parallel pattern.

Furthermore, the magnetism-shielding member 75 or a combination of themagnetism-shielding member 75 with a member 78 composed of non-magneticsubstance (for example, aluminum) may be disposed as themagnet-supporting member on the side wall of the developer vessel sothat the angle of the magnet mechanism can be adjusted. In addition, themagnetic carrierpeeling position Pf can be made closer to the developingposition Pd, if, as illustrated in FIG. 4, the magnetism-shieldingmember 75 is disposed to cover the opposite side pole S of the magneticbrush-forming magnet 73 and the side portion of the pole S positioned onthe side where the developer-pumping magnet 74 is provided, and if atthe same time as illustrated in FIG. 5, the magnetism-shielding member75 is disposed to cover the side portion of the pole S positioned on theside opposite to the side where the developer-pumping magnet 74 isprovided.

In the developing apparatus shown in FIGS. 3 to 5, a brushlength-adjusting mechanism 79 is disposed in the vicinity of themagnetic brush-supporting surface of the magnetic brush mechanism 70,i.e., the surface of the developing sleeve 71, between thedeveloperpumping position P, of the magnetic brush mechanism and thedeveloping position Pd where the magnetic brush is brought into contactwith the electro-static image-carrying surface 5. This brushlength-adjusting mechanism 79 comprises a sharp edged blade 80 and aslide member 82 mounted movably along the bottom face of the developervessel 68 on a supporting seat 81 provided on the bottom face of thevessel 68.

This slide member 82 includes slots 83 extending in a direction normalto the axis of the magnetic brush mechanism 70. Screws 84 are fitted tothe supporting seat 81 through said slots 83, allowing the brushlengthadjusting mechanism 79 to be adjusted. In addition to theseadjustment members, any other known mechanisms can be optionally used toadjust the position of the blade edge 80 of the brush length-adjustingmechanism.

The adjustment of the position of this brush lengthadjusting mechanism79 is performed in the following manner by the above-mentionedadjustment mechanism.

a. The distance a between the blade edge 80 of the brushlength-adjusting mechanism 79 and the magnetic brush-supporting surface(the surface of the sleeve 71) is made shorter than the distance dbetween the magnetic brush-supporting surface and the bottom face of thedeveloper vessel at the develeper-pumping position P,,.

b. The distance d between the electro-static imagecarrying surface 5 andthe magnetic brushsupporting surface at the developing position P, ismade a little shorter than the distance d between the blade edge 80 ofthe brush length-adjusting mechanism and the magnetic brush-supportingsurface.

The distance d;, between the electro-static imagecarrying surface 5 andthe magnetic brush-supporting surface is varied considerably dependingon the kind of the electro-static image-carrying surface. For instance,a good image is obtained when in the case of a zinc oxide photosensitivelayer the distance d;, is about 4 mm and in the case of a cadmiumsulfide photosensitive layer the distance d is about 2 mm. The distanced; can be easily adjusted as desired, for example, by mounting theentire developing device or the magnetic brush member movably withrespect to the sensitive drum. The distance d between the magneticbrush-supporting surface and the bottom face of the developer vessel ismade longer than the distance d so that at the developer-pumpingposition Pp the pumping of the developer can be readily accomplished anda fresh developer can be sufficiently supplied at said pumping positionP The distance d, between the blade edge 80 of the brushlength-adjusting mechanism and the magnetic brushsupporting surface ismade a little longer than said distance d More specifically, thedistance d is so set that the value of (d, d is generally 0 to 2 mm,especially about 0.5 mm.

When the distance d between the tip point of the bush-length-adjustingmechanism and the magnetic brush-supporting surface is adjusted in theforegoing manner, the developer 0 pumped at the developerpumpingposition P, and transported therefrom is brought into a slidable contactwith the blade edge 80 of the brush length-adjusting mechanism and theexcessive portion of the developer is removed. Accordingly, a magnetictoner provides magnetic brush of uniform density and a uniform length atthe developing zone Pd. An appropriate amount of a developing toner isalways stably and uniformly transported to the developing zone Pd. (Theamount of the developing toner transported is not so excessive as willcause excessive application of the toner on the electrostaticimagesupporting face and is not so scarce as will cause insufficientapplication of the toner on the electro-static image-supporting surface.Furthermore, by adjusting the above distance d within a specific rangein relation to the clearance d at the developing zone Pd, a light, sureand uniform contact can be attained between the magnetic brush and theelectro-static image-carrying face at the developing position Pd,whereby the electrostatic image can be developed faithfully.

In the magnetic brush mechanism 70, it is preferred that a substantiallyparallel magnetic brush is formed at the above-mentioned developing zonePd. In this case, the toner powder can be tightly and uniformlycontacted with the electro-static image-carrying surface 5 according tothe magnetic brush. In order to attain this feature, as is illustratedin FIG. 6, a developing counter pole 84 may be disposed in thesubstantially stationary state in the vicinity of the inner face of theportion of the photosensitive drum 6 confronting the magnetic brushmechanism 70.

In order to dispose the developing counter pole 84 in the substantiallystationary state in the vicinity of the inner face of the photosensitivedrum 6, the developing counter pole 84 is attached to one end of an arm85, both ends of which are directed downwardly, and a balancing weight86 is attached to the other end of this arm 85. The central portion ofthe arm 85 is engaged with or fitted to the rotary shaft 87 of thephotosensitive drum 6, so that the arm is freely hanging down from theshaft 87. Thus, even when the photosensitive drum 6 supported on theends of the shaft is rotated, off the weight 86 the developing counterpole 84 can be always located to align the magnetic mechanism 70 withthe developing position Pd. When the photosensitive drum is supported inthe open side manner on one frame of the machine housing, the developingcounter pole 84 is fixed to the other frame of the machine housing. Thisenables the developing counter pole 84 to always confront the magneticbrush mechanism at the developing position. When the developing counterpole 84 is disposed in the vicinity of the inner face of thephotosensitive drum in the foregoing manner to confront the magneticbrush mechanism at the developing position, the caring of the magneticbrush can be always kept parallel in the vertical direction andmaintained in good conditions, and at the same time, the effective areacan be enlarged at the developing zone Pd. Alternatively, the substrateof the photosensitive drum may be composed of a magnetic substance, butsince the magnetic flux extends in a broad region, the magnetic carrieris adsorbed on the surface of the photosensitive drum 6 and it istransported to the transfer zone and other treatment zones in the stateabsorbed on the drum surface, which results frequently in bad influenceson the image. It is also possible to wind a thin magnetic substance onthe inner face of the photosensitive drum, but when this is done, themagnetic resistance is too great and the intended effects cannot beobtained. In the foregoing embodiment of this invention, by disposingthe developing counter pole 84 to meet the abovementioned positionalrequirements, it is possible to reduce the magnetic resistance and toattain the desired effects.

The supply of the developing toner will now be described by referring toFIG. 3 again.

In the upper portion of the developer vessel 68 forming one chamber, aninlet 90 (see FIG. 6) is provided to insert a cylindrical cartridge 89for supply of a toner into the side wall 88 of the developer vessel, anda supporting member 91 is provided on a toner supply chamber 93 tosupport rotatably the cartridge 89 inserted from the inlet 90. Thistoner supply chamber 93 is separated through partition walls 94 and anopening 92 is provided on the lower partition wall.

The toner supply cartridge 89 comprises, for instance, as illustrated inFIG. 7, a cylinder 97, both ends 95, 95' of which are closed and whichis provided with an opening 96 scalable and openable along thesubstantially entire length of the cylinder. A toner power is containedin the cylinder. The opening 96 of the cylinder 97 includes outlets ofsuch configuration and dimension that when the sealing of the opening isreleased and the opening faces downwardly, the toner powder 0 containedin the cylinder is discharged uniformly along substantially the entirelength of the cylinder. At such outlet, there may be positioned, forinstance, slit-like openings formed along the entire length of thecylinder and a number of holes distributed along the entire length ofthe cylinder. At least part of at least one of the side walls 95, 95 ofthe cylinder is made of a transparent or semi-transparent material sothat the toner contained in the cylinder can be observed from theoutside. On this portion 95 or 95 of the cylinder a mark 98 is providedindicating the position of the opening 96. The mark may be an arrow,letter, figure, projection or convexity. The opening 96 of the cartridge89 may be sealed by adhesive tape 99 or the like, or outside edges ofthe opening 96 may be integrally formed with the cylinder through acuttable perforated line or the like.

In supplying a toner into the toner supply chamber 93, the opening 96 ofthe cartridge 89 initially faces upwardly, and in this orientation theopening 96 is unsealed. Then, while maintaining the cartridge in thisstate, it is inserted into the interior of the toner supply chamber 93through the inlet 90 provided on the side wall 88 of the developervessel. The cartridge 89 is then rotated 180, whereby the opening 96 ofthe cartridge faces downwardly and a necessary amount of the toner issupplied into the toner supply chamber 93.

When the toner supply cartridge 89 as shown in FIG. 7 is employed, thesupply of the toner into the developing apparatus 13 can be accomplishedvery easily without contaminating hands of a machine operator orscattering fine toner powder. Further, provision of the mark 98indicating the position of the opening 96 on the side edge portion 95 or95' of the cylinder makes it possible to conduct unsealing of theopening 96 easily without mistake, and insertion of the cartridge intothe toner supply chamber 93 and supply of the toner by turning thecartridge to the prescribed position can be performed very easily withcertainty. Moreover, it is easy to confirm whether the cartridge islocated correctly at the toner supply position. Moreover, since the sideedge portion or 95 of the toner supply cartridge 89 is composed of atransparent or semitransparent material, the amount of the tonercontained in the cartridge can be easily confirmed from the outside andhence, the supply of the toner can be accomplished promptly withoutdelay. In order to facilitate insertion and turning of the cartridge 89,it is generally preferred that the cylinder of the toner supplycartridge and the inlet 90 have a circular form, but when the inlet 90is constructed of an individual member rotatable on the side wall of thedeveloper vessel, they may take any other optional form.

In order to prevent the toner from scattering into the outside andensure the support of the cartridge while preventing shaking of thecartridge, it is preferred that a packing member 100 of planted hairs orsponge be provided along the periphery of the inlet 90.

In the embodiment shown in FIG. 3, at the position of the opening 92provided in the lower portion of the toner supply chamber 93, there isrotatably mounted a toner supply roller 102 having grooves 101 on thesurface thereof. On the lower end portion of the partition wall 94, endsof elastic members 103 are fixed. The elastic members 103 are composedof a flexible material such as a Mylar film. The free ends of theelastic members 103 are allowed to make contact with the peripheralsurface of the toner supply roller 102.

When the toner supply roller 102 is stopped, the toner supply chamber 93and a developing chamber 104 are in an enclosed state. When the tonersupply roller 102 is rotated in the clockwise direction, the tonercontained in spaces of the grooves 101 is fed into the developing room104. The afore-mentioned agitation mechanism 69 is disposed below thetoner supply roller 102, and it frictionally charges the freshlysupplied toner while mixing it with the magnetic carrier. The resultingdeveloper composition is then fed to the developer-pumping position ofthe magnetic brush mechanism 70 by means of the agitation mechanism 69.

In the foregoing manner, in the toner supply mechanism illustrated inFIG. 3, an appropriate amount of a toner powder is freshly supplied byrotating manually or automatically the toner supply roller 102 afterobtaining a prescribed number of copies. An advantage to thistoner-supplying operation is that it can be accomplished without takingthe development mechanism 13 from the machine housing.

Transfer Mechanism As is illustrated in FIG. 8A, the transfer mechanism36 used in this embodiment comprises a transfer roller 107 including aroller base 105 composed of an electrically conductive rubber or otherelectric conductive material such as a metal and an insulating thinlayer 106 which is coated on the roller base 105, and an electric source109. The transfer roller 107 is disposed to press transfer paper 12against the surface layer 5 of the photosensitive drum 6, and theelectric source 109 is provided to apply a voltage between theelectrically

1. An electrostatic photographic copying apparatus comprising: a framedefining a housing with a top surface having a transparent plate onwhich an original to be copied is placed, a rotatable photosensitivedrum for rotation in one direction as the apparatus copies having anelectrostatic photographic material on the periphery thereof, animage-forming zone disposed adjacent to the periphery of saidphotosensitive drum for forming on said photosensitive material anelectrostatic latent image corresponding to the image of the originaland a developed image corresponding to the latent image, a transfer zonefor transferring said image to a transfer paper, and a transfer paperforwarding system for feeding the transfer paper on which the image hasbeen transferred to said transfer zone and through a desired treatingzone to a discharge end; wherein said photosensitive drum is disposedwithin the housing with the top of the periphery thereof approaching andconfronting an inner surface of the top plate of the housing adjacent alocation on the inner surface; wherein said transfer zone is positionedat an angle exceeding 180* in the direction of rotation of thephotosensitive drum from the location on the inner surface of the topplate; wherein said transfer paper forwarding system forwards a transferpaper in a substantially linear, upwardly inclined passage extendingfrom an inlet end through the transfer zone to the discharge end;wherein said inlet end is preceded by a nip roller adjacent thereto;wherein said image forming zone includes at least one charging memberfor electrically charging said photographic material, an optical systemfor projecting an image of the original onto the surface of thephotographic material and a developing device for developing theelectrostatic latent image formed on said photographic material whichare all housed within a first area defined on at least three sides ofthe top surface of said housing, the circumferential surface of thephotosensitive drum extending from the top thereof to the transfer zonein the direction of rotation of the photosensitive drum and the transferpaper forwarding system; and wherein a transfer paper removing memberand a photosensitive drum cleaning member are housed within a secondarea defined on at least three sides by the top surface of the housing,the circumferential surface of the photosensitive drum which extendsfrom thE top of the photosensitive drum to the transfer zone in adirection opposite to the direction of rotation of the photosensitivedrum and by the transfer paper forwarding system.
 2. The apparatus ofclaim 1, wherein said transfer paper forwarding system includes meansfor feeding a continuous web of transfer paper to said nip roller, acutting device for cutting the continuous web, an insertion opening fora separated sheet-like transfer paper, means for feeding the sheet-liketransfer paper inserted from said insertion opening to said nip rollerand means for bringing the web of transfer paper and sheet-like transferpaper into contact with the surface of the photographic material.
 3. Theapparatus of claim 2, wherein said means for feeding the sheet-liketransfer paper feeds the paper into an extension of the substantiallylinear, upwardly inclined passage from said insertion opening to saidnip roller, wherein said passage and said extension combine to make asingle, continuous linear passage, whereby the sheet-like transfer paperis forwarded substantially linearly from said insertion opening to saiddischarge end.
 4. The apparatus of claim 3, wherein said transfer paperforwarding system includes a synchronizing transfer roller provideddownstream of the insertion opening, a sheet-like transfer paperdetecting switch provided adjacent to the nip position of thesynchronizing transfer roller, a drive system for rotating saidphotosensitive drum at substantially the same speed as the transferspeed of the sheet-like transfer paper, a switch means which emits asignal upon detecting arrival of a forward edge of an area of thephotosensitive drum on which an image is formed, said switch means beingspaced from a position of contact between the photosensitive drum andthe sheet-like transfer paper by a distance equal to the distancebetween said contact position and the sheet-like transfer paperdetecting switch in a direction opposite to the direction of rotation ofthe drum, means for stopping rotation of said synchronizing transferroller when the leading edge of the sheet-like transfer paper hastouched the detecting switch and for resuming rotation thereof inresponse to the signal from said switch means, whereby the leading edgeof the sheet-like transfer paper reaches the transfer zone insynchronization with the forward edge of the area on the photosensitivedrum on which an image is formed.
 5. The apparatus of claim 1, whereinthe transfer paper is dispensed from a roll in a continuous web, whereinsaid roll is contained in a space adjacent said first area to place saidfirst area between said drum and said roll.
 6. The apparatus of claim 5,wherein means are provided for feeding separate sheets of the transferpaper and wherein said means includes a downwardly directed linearextension of said upwardly inclined passage positioned upstream of saidnip roller, said extension extending below said space in which said rollis contained.
 7. The apparatus of claim 1, wherein a substantially emptyspace is provided in said housing below said upwardly inclined passage,said space extending downstream of said transfer zone to said dischargeend to facilitate access to said transfer passage.
 8. The apparatus ofclaim 7, wherein said discharge end is positioned in a plane above thebottom of said drum.